Light emitting device for AC power operation

Abstract

Disclosed is an improved light-emitting device for an AC power operation. A conventional light emitting device employs an AC light-emitting diode having arrays of light emitting cells connected in reverse parallel. The arrays in the prior art alternately repeat on/off in response to a phase change of an AC power source, resulting in short light emission time during a ½ cycle and the occurrence of a flicker effect. An AC light-emitting device according to the present invention employs a variety of means by which light emission time is prolonged during a ½ cycle in response to a phase change of an AC power source and a flicker effect can be reduced. For example, the means may be switching blocks respectively connected to nodes between the light emitting cells, switching blocks connected to a plurality of arrays, or a delay phosphor. Further, there is provided an AC light-emitting device, wherein a plurality of arrays having the different numbers of light emitting cells are employed to increase light emission time and to reduce a flicker effect.

What is claimed is: 
     
       1. A light-emitting device, comprising:
 a first power source connection terminal and a second power source connection terminal; and 
 a plurality of first arrays of GaN-based light emitting cells, each first array comprising a plurality of serially connected light emitting cells, the first arrays being connected in parallel to one another between the first power source connection terminal and the second power source connection terminal, and each first array being configured to emit light under a different voltage level from the other first arrays, 
 wherein the GaN-based light emitting cells are monolithically formed on a substrate, and 
 wherein an N-type semiconductor layer of one light emitting cell is electrically connected to a P-type semiconductor layer of an adjacent light emitting cell. 
 
     
     
       2. The light-emitting device of  claim 1 ,
 wherein the first arrays have different numbers of light emitting cells from each other. 
 
     
     
       3. The light-emitting device of  claim 2 , further comprising:
 a plurality of first resistors connected in series to the first arrays, 
 wherein each first resistor is respectively connected to one of the first arrays. 
 
     
     
       4. The light-emitting device of  claim 3 ,
 wherein the first resistors have different resistance values from each other, and 
 the first resistors are respectively connected in series to the first arrays in such a manner that one of the first resistors comprising a larger resistance value relative to the other first resistors is connected to a first array comprising a smaller number of light emitting cells relative to the other first arrays, and one of the first resistors comprising a smaller resistance value relative to the other first resistors is connected to a first array comprising a larger number of light emitting cells relative to the other first arrays. 
 
     
     
       5. The light-emitting device of  claim 1 , further comprising:
 a plurality of second arrays of light emitting cells, each second array comprising a plurality of serially connected light emitting cells, the second arrays being connected in reverse parallel to the first arrays. 
 
     
     
       6. The light-emitting device of  claim 1 , wherein the substrate consists of Al 2 O 3  or SiC. 
     
     
       7. A light-emitting device, comprising:
 a bridge rectifier; and 
 a plurality of light emitting cell arrays, each array comprising a plurality of serially connected GaN-based light emitting cells, the arrays being connected in parallel to one another between two nodes of the bridge rectifier, and each array is configured to emit light under a different voltage level from the other arrays, 
 wherein the GaN-based light emitting cells are monolithically formed on a substrate, 
 wherein the bridge rectifier comprises a bridge circuit in which at least one diode is disposed between a first node and a second node, at least one diode is disposed between the second node and a third node, at least one diode is disposed between the third node and a fourth node, and at least one diode is disposed between the fourth node and the first node of the bridge circuit, respectively, and 
 wherein each diode comprises a light emitting cell. 
 
     
     
       8. The light-emitting device of  claim 7 ,
 wherein each array comprises a different number of light emitting cells than the other arrays. 
 
     
     
       9. The light-emitting device of  claim 8 , further comprising:
 a plurality of resistors connected in series to the arrays, 
 wherein each resistor is respectively connected to one of the arrays. 
 
     
     
       10. The light-emitting device of  claim 9 ,
 wherein the resistors have different resistance values from each other, and 
 wherein the resistors are respectively connected in series to the arrays in such a manner that one of the resistors comprising a larger resistance value relative to the other resistors is connected to an array comprising a smaller number of light emitting cells relative to the other arrays, and one of the resistors with a smaller resistance value relative to the other resistors is connected to an array comprising a larger number of light emitting cells relative to the other arrays. 
 
     
     
       11. The light-emitting device of  claim 7 , wherein the bridge rectifier and the plurality of light emitting cell arrays are formed on a substrate. 
     
     
       12. The light-emitting device of  claim 11 , wherein the substrate consists of Al 2 O 3  or SiC.